1. Field of the Invention
The present invention relates to an ink set for ink-jet recording, an ink-jet recording apparatus which accommodates the same, and a method for producing the ink set.
2. Related Art
In the ink-jet recording system, ink droplets are formed by using a variety of ink discharge methods including, for example, the electrostatic attraction method, the method in which mechanical vibration or displacement is applied to the ink by using a piezoelectric element, and the method in which bubbles are generated by heating the ink to utilize the pressure generated thereby, and all or a part of the ink droplets are adhered to an objective recording material such as paper to perform the recording.
Those known as the ink for ink-jet recording to be used for the ink-jet recording system as described above include those obtained by dissolving or dispersing water-soluble dyes or pigments in water or a liquid medium composed of water and a water-soluble organic solvent. When the water-soluble dye and the pigment are compared with each other, then the water-soluble dye is inferior in water resistance as the water-soluble dye is completely dissolved in the ink medium, and the water-soluble dye is fairly inferior in weather resistance as well in view of the chemical structure thereof. On the contrary, the pigment is extremely satisfactory in weather resistance such as water resistance as the pigment is dispersed to prepare the ink because the pigment is not dissolved in the ink medium. Therefore, in recent years, the change progressively occurs such that the pigment ink is dominantly used as the ink for ink-jet recording rather than the dye ink.
It is required for the ink for ink-jet recording that the ink for ink-jet recording has the most appropriate performance characteristics to be used for the ink-jet recording method. Specifically, for example, the following features are required. That is, the printing quality is satisfactory, and neither precipitation nor aggregation is caused even when the ink for ink-jet recording is not used for a long period of time. No clog-up occurs in the ink flow passage or at the tip of the head of the ink-jet printer, and the ink for ink-jet recording is excellent in weather resistance.
Recently, it is demanded to obtain a printing quality equivalent to that of the picture image, for which a variety of improvements have been made in order to suppress the blur at the boundary between different colors, i.e., the so-called bleeding. For example, Japanese Patent Application Laid-open No. 10-95941 discloses a technique in which glycol-based butyl ether, which is represented by triethylene glycol monobutyl ether, is used as a permeating agent for a water base ink. It is considered that the glycol-based butyl ether has an effect to suppress the bleeding, because the velocity of permeation of the glycol-based butyl ether into the paper is faster than those of surfactants or the like which are commonly used permeating agents. On the other hand, when the glycol-based butyl ether is added in an amount necessary to obtain the effect to quicken the permeation velocity into the paper, then the surface tension of the ink for ink-jet recording is lowered, and a function appears to promptly cause the blur on the paper surface as well. Therefore, the effect to suppress the bleeding is not sufficiently obtained.
As described above, the conventional ink for ink-jet recording has involved the following problem. That is, it is impossible to suppress the bleeding sufficiently to such an extent that a printing quality of extremely high image quality, which is equivalent to that of the picture image, is successfully obtained.